Convert Class Object to NSData Which Does Not Conform to NSCoding

Question

This is a follow up to a previous question that went unanswered: Swift EKCalendar not persisting

Previous Post Summary: In a nutshell, I can create new EKCalendars, save them to the EventStore, and event write events to them. However once the app goes into the background the EKCalendars are deleted or removed from memory. Since figuring out how to make the calendar persist in the EventStore is starting to seem like its not an option, I'm exploring some alternatives.

Thoughts: One idea was to store the EKCalendars in the UserDefaults as well as save them to the EventStore. After looking into it a little i found very helpful posts such as this one: Save custom objects into NSUserDefaults in which they convert a custom object to NSData and then store it. Unfortunately for me, EKCalendar does not conform to the NSCoding protocol, and as far as i know, there is no way to extend the class to do so?

Question: Is there a way to convert an EKCalendar object, which does not conform to the NSCoding protocol, into NSData? Or is there a way to save the class objects location some other way?

Side Note: To avoid overlap on the questions, if you have any info about making the EKCalendar persist in the EventStore please post those responses in previous post link at the top.

Answer 1

So I've worked with objects that conformed to NSCoding before, so I thought I would give you a potential solution and see if it works for you.

Disclaimer:

Keep in mind, I am not 100% sure if this is legal to do, but it made sense in my mind so I thought I would share. This solution also may miss a requirement that you need for your project, and if so let me know.

Alright, so basically my thought was that you could create a subclass of EKCalendar that conforms to NSCoding. This would look something like this:

class MyCalendar: EKCalendar, NSCoding {
    ...
}

Now that is the biggest leap of faith, but after that you should just be able to include the methods required for this custom class to conform to NSCoding. This would look something like this.

class MyCalendar: EKCalendar, NSCoding {

    init(color: CGColor){ //you can include your own init if you want, or just use the superclass init
        super.cgColor = color
        ...
    }

    required init?(coder aDecoder: NSCoder) {
        super.init()
        super.cgColor = aDecoder.decodeObject(forKey: "Color") as! CGColor
        ...
    }

    func encode(with aCoder: NSCoder) {
        aCoder.encode(super.cgColor, forKey: "Color")
        ...
    }
}

This is a slightly circuitous method since you will have to encode and decode all the properties that you want to store, but to be fair that is true for any custom class that you want to make conform to NSCoding.

You will also have to do all the directory stuff for where your plist is stored, but that should just involve a simple search on SO.

Other than that, let me know if this works for you.

Edit

So as I suspected, I think the above approach is "illegal" and so it was giving some errors when I was trying to call the super.init for EKCalendar.

My next best solution, that is not quite as elegant, is to create the same custom object, but this time it is a subclass of NSObject instead. Then this object has an EKCalendar property that you can use:

class MyCalendar: NSObject, NSCoding {

    var ekCalendar: EKCalendar

    init(entityType: EKEntityType, eventStore: EKEventStore){
        ekCalendar = EKCalendar(for: entityType, eventStore: eventStore)

    }

    required init?(coder aDecoder: NSCoder) {
        ekCalendar = aDecoder.decodeObject(forKey: "Calendar") as! EKCalendar

    }

    func encode(with aCoder: NSCoder) {
        aCoder.encode(ekCalendar, forKey: "Calendar")

    }
}

I would say the benefit to this approach would be that you don't have to encode and decode all of its properties, since you should just be able to do something like this:

var calendar = MyCalendar(//initialize)
calendar.ekCalendar.cgColor = UIColor.black.cgColor //just an example